The Effects of Aspirin in Gestation and Reproduction (EAGeR) Trial is a multi-site, prospective doubleblind randomized controlled trial designed to assess the effects of low-dose aspirin in combination with folic acid treatment on pregnancy and gestation among 1228 women with a history of 1-2 pregnancy losses. A large biospecimen repository is available for analysis and offers a good platform for testing multiple hypotheses. This statement of work is for the measurement of stored biospecimens in the EAGeR Trial. The proposed assays will provide a rich data source on biomarker levels that can answer novel research questions in conjunction with the extensive data already collected in the EAGeR Trial. A growing body of evidence suggests that exposure to many common environmental chemicals, particularly those with endocrine-disrupting properties, may be associated with impaired fecundability and increased risk of adverse pregnancy outcomes. However, much of the findings to date have been equivocal. There is a need to further investigate the potential role of environmental chemical exposures in leading to adverse reproductive and gestational outcomes, particularly among prospective studies with gold standard ascertainment of reproductive and pregnancy outcomes. Due to much prior research being conducted among individuals with occupational exposure, there is also a need for additional research among healthy adults with similar exposure levels to the general population, to ascertain whether background exposure to key environmental chemicals may pose reproductive health risks. Finally, although phenols, such as BPA, and phthalates are known endocrine disruptors, few studies have evaluated their association with reproductive outcomes. There is also a great need for research on emerging endocrine disruptors, including parabens and benzophenones, and reproductive outcomes.